1. Field of the Invention
The present invention relates to a display system of the dot matrix type, and a display method therefor. More particularly, it relates to a method of driving a display system for presenting multicolor/multiple-tone (or polytonal) displays, and a system therefor.
2. Description of the Related Art
An LC (liquid-crystal) display system in the prior art displays an image in such a way that interface signals received as external inputs are converted into drive signals for driving the LC display system, the drive signals are delivered to LC drive means, and the LC drive means accepts for 8-level display data among the delivered drive signals every horizontal line of a frame and then applies the accepted data to an LC panel as 8-level LC drive voltages conforming to the display data. With this mode, 8 tones or gradations are displayed by the 8-level voltages divided uniformly or equally, as stated in "Lecturing thesis C-480", the Spring National Meeting of the Institute of Electronics, Information and Communication Engineers of Japan, 1991.
FIG. 5 of the accompanying drawings illustrates the circuit arrangement of an 8-level uniform applied LC voltage generator (a generator by which the 8-level uniform voltages to be applied to the LC panel are produced) in the prior art. Numeral 27 indicates an LC driving supply voltage, which is divided into the 8-level voltages by resistors 28-36. Operational amplifiers 37-44 are respectively connected to the nodes of the adjacent resistors 28-36. Herein, the 8-level uniform voltages 22 to be applied to the LC panel (8-level voltages V1-V8) are produced by equalizing all the resistances of the resistors 29-35. The values of the voltages V12-V8 on this occasion are listed in Table 1 below. As can be understood from this table, all the voltage differences between the respectively adjacent levels are 0.7 [V].
TABLE 1 TONE VOLTAGE VALUE [V] #1 6.50 #2 5.80 #3 5.10 #4 4.40 #5 3.70 #6 3.00 #7 2.30 #8 1.60
FIG. 8 is a diagram showing an example of the relationship between the applied voltage to the LC panel and the display intensity or brightness of this LC panel in the prior art. The levels of the display intensity correspond respectively to the 8-level applied LC voltages V1-V8 obtained by uniformly dividing the supply voltage 27. In the illustrated graph, the display intensity levels are plotted on a logarithmic scale.
In this manner, the 8-level applied LC voltages are based on the uniform voltage division in the prior-art example. The uniform LC voltages incur the problem that the displayed tones are not always seen uniformly or in a well-balanced manner by the human eye.